Updated SWMP

1.4.       Further Advice
Further advice was received from Noosa Council, dated 7 November 2023, regarding the development
application (RAL23/0013). The further advice letter asks for the proposal to comply with the Noosa Plan for
stormwater items listed below.

Issue - Stormwater Quality
It is unclear how compliance with the pollutant load reduction targets has been calculated. The scheme requires
an 80%/60%/45% reduction in TSS/TP/TN for the unmitigated development site loads. Since the bioretention
device receives flows from areas outside the development, a manual calculation of compliance with this target is
required, based on the MUSIC model results.

This is achieved by:

1.   Extracting the development site (current and original developments) source loads from the model
2.   Calculating the required pollutant load removal by multiplying (1) by 80%/60%/45%
3.   Comparing the required load removal (kg/yr) to the actual load removal achieved by the device

This does not appear to have been done.

Response:

The SMP demonstrates an 80%/60%/45% reduction in TSS/TP/TN for the unmitigated development site
loads according to the scheme as summarized in Table 3-7 and Table 3-8.

The information provided in the SMP-V2 has been reformatted as per the above request:

1.   The source loads of the current and original developments were extracted from the model (refer
     Figure 1-3) and are summarized in the “Unmitigated (kg/yr)” column of Table 1-1.
     Note that there is a minor difference between Figure 1-3 and Table 3-7 as MUSIC is a stochastic model, with
     randomness resulting in minor changes in results between model runs.
2.   The required pollutant load removal (2) was calculated by multiplying (1) by 80%/60%/45%. This
     information is provided in Table 1-1.
3.   The actual load removal (3) achieved by the device exceeds the required load removal (2) and therefore
     meets the target reductions as per the scheme.




23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona                                Page 13